The invention relates to a two-phase fusible interlining and to a process for its manufacture.
In general, fusible interlinings must be capable of being stored after the textile substrate has received the layer of polymers and are intended, owing to the effect of the change in an external parameter, to become adhesive, thus enabling them to adhere to another fabric.
Fusible products are now commonly employed in the textile industry, for example as reinforcing fabrics, their application to linings or to draperies making it possible to modify the characteristics of the fabrics, improving their behaviour and their liveliness. The textile substrates used are very varied. They may be woven, knitted or nonwoven.
The methods of application of the adhesive layer to its substrate are numerous. For many uses, an application using spots, which allows the fabrics to retain a great flexibility, is preferred, whereas for other uses a continuous layer of adhesive enables the required properties to be attained more satisfactorily.
In the case of reinforcing fabric, the textile substrate is coated with the fusible substance. At present, this coating is in most cases a coating using spots produced with the aid of an engraved roll. The fusible polymers, initially in powder or paste form, are heated to a temperature which enables them to melt and to adhere to the substrate. According to another technique, the coating is produced by transfer, that is to say that the fusible polymers are deposited in spot form by a printing roll onto a carpet treated to be nonadhesive; these spots are then transferred at a lower temperature onto the textile substrate.
The fusible interlining thus obtained is then stored at room temperature. It is then necessary that the various layers of this product, when in contact, should not adhere to each other. The fusible interlining must not exhibit stickiness and adhesive properties ("tack") at room temperature.
During this storage it is also necessary that the aging process of the product should not interfere with its adhesive properties which are necessary for the subsequent bonding.
The fusible interlining is therefore employed by manufacturers who apply it against other fabrics, draperies or linings, and thus produce the adhesive bonding of the reinforcing fabric to the drapery with the aid of a press at pressures of a few decibars to a few bars for relatively short times of the order of 10 to 30 seconds and at temperatures which are generally higher than 100.degree. C. During this stage the polymers of the fusible interlining must regain their adhesiveness. However, they must not have a viscosity which is too low for too long a time during this operation because otherwise the polymers pass through the textile substrate or the drapery, giving rise to backflow and break-through problems which make the products obtained relatively unattractive and frequently unusable.
Finally, the finished garments and therefore, in particular, the draperies or linings provided with reinforcing fabrics must stand up to the different methods of use, washing, ironing and the like. The bonding produced in the preceding stage must therefore withstand difficult environments.
Many attempts have been made to produce products which are well-suited to the different constraints resulting from the combination of the stages referred to above.
Thus, it has been proposed, for example, to produce an adhesive consisting of two or a number of layers of polymers of different physical characteristics. By suitably choosing the viscosity and the melting temperature of these different layers it is thus possible to limit the break-throughs or the backflows (documents FR-A-2,318,914, DE-A-2,461,845, FR-A-2,576,191). However, the use of these techniques shows either a lack of mechanical cohesion of the two polymer layers or processing difficulties which are difficult to overcome, or poor uniformity of the second layer.
Document FR-A-2,023,354 describes a heat-weldable double lining consisting of a textile structure coated on at least one of its faces with a polymer or a mixture of polymers which is essentially uncrosslinked at the time of the application. At least a fraction of this coating is converted by heating into insoluble plastic and exhibits a porous or foam structure at least at the time of the heat-welding.
More recently, the document U.S. Pat. No. 3,937,859 describes a thermoplastic/thermally crosslinking composition in which the thermoplastic part is a copolymer of olefin and of vinyl chloride. The presence of chlorine, a hyperreactive polymerisation site, gives rise to problems with regard to the control of the routing of the crosslinking reaction and consequently results in poor aging of the textile product.
It emerges that the use of fusible interlinings is confronted with the following problems:
interpenetration of the two layers, during the coating, by mixing of the base of the spot of the upper layer with the top of the spot of the underlayer; PA1 hardening of the textile when the coating is too great in weight; PA1 difficult control of the rate and degree of progress of the crosslinking reaction of the reactive system and of the aging of the fusible interlining at the time of storage. PA1 (i) at least one adhesive system in the form of a thermoplastic powder of dense granules whose main function is to ensure the adhesion of the fusible interlining to the drapery at the time of the bonding; PA1 (ii) at least one crosslinkable system comprising at least one crosslinkable resin and at least one hardener, in the form of a homogeneous matrix whose main function is to coat the granules of thermoplastic powder of the bonding system. PA1 a crosslinkable system comprising at least one crosslinkable resin and at least one hardener is prepared in the form of a homogeneous matrix; PA1 the coating paste is prepared by dispersing a thermoplastic powder in the said matrix; PA1 the coating paste thus prepared is applied onto a textile substrate by coating using spots on a rotary frame; PA1 the whole is subjected to a drying temperature lower than that of the onset of crosslinking; PA1 at the time of the bonding of the fusible to the drapery, the crosslinking reaction is set in motion by passing continuously through a press heated to a temperature of the order of 130.degree. C., at a pressure of a few bars and for a relatively short time of the order of 15 seconds; PA1 the crosslinking reaction is completed by passing the fusible-drapery composite through an oven heated to a temperature of the order of 150.degree. C. for a period of between of the order of 30 to 60 seconds. PA1 the particles of the thermoplastic powder, which are perfectly coated and bound by the crosslinkable system, act as a filler which makes it possible to keep the whole at a sufficiently high viscosity to avoid its entry into the textile substrate. PA1 drying of the fusible interlining at a temperature below the crosslinking temperature makes it possible to slightly soften the thermoplastic powder which remains in the form of granules and to bond the adhesive layer sufficiently to the textile substrate. PA1 the strong presence of imine (--NH) functional group in the modified melamine, besides reactive groups (hydroxyl, carboxyl and the like) in the crosslinkable resin, imparts a high reactivity to the crosslinkable system of the adhesive layer of the fusible interlining. PA1 the increase in bond strength; PA1 the elimination of break-throughs with steam; PA1 good resistance of the fusible-drapery composite to steaming-dry cleaning cycles without the least blistering; PA1 good resistance to washing at high temperature above or equal to 45.degree. C. PA1 at least one adhesive system in the form of a thermoplastic powder with dense granules whose main function is to ensure the adhesion of the fusible interlining to the drapery at the time of the bonding; PA1 at least one crosslinkable system comprising at least one crosslinkable resin and at least one hardener, in the form of a homogeneous matrix, whose main function is to coat the granules of thermoplastic powder of the adhesive system. PA1 on the one hand, they enable the adhesive layer to bond onto the textile substrate; PA1 on the other hand, these granules of thermoplastic powder, perfectly coated and bonded by the crosslinkable system, act as a filler which makes it possible to keep this system at a sufficiently high viscosity to avoid and minimise its entry into the textile substrate.